This invention relates to electrical connectors, and more particularly, to an improved modular connector for use in data communications and/or telephony.
Modular connectors, such as the popular RJ 45 connector, are well known in the communications art. FIGS. 1A and 1B show a typical male modular connector 12, known as the xe2x80x9cplugxe2x80x9d, and typical female modular connector 14, known as the xe2x80x9cjackxe2x80x9d. The plug 12 and the jack 14 connectors mate for communicating signals between the external circuit 16, in this instance a printed circuit board, and the external circuit 18, in this instance a computer. The pins 20 of the jack 14 electrically connect to the printed circuit board, and the cable 22 electrically connects the plug 12 to the computer.
FIG. 1B shows a perspective view of the plug connector 12 and a partially cut away view of the jack connector 14. The plug connector 12 includes a body 24, and disposed with the body 24 are a plurality of conductors 28 that include blade-type contacts 30. The jack connector 14 can include the body 32, which in turn can include a housing 34 and a lead frame 36. The plurality of conductors 38 is disposed with the body 32, and each of the conductors of the plurality include a contacting portion for contacting the contacts 30 of the plug connector 12 when the plug connector 12 is mated with the jack connector 14. The reference numeral 40 indicates generally the row of contact portions of the plurality of connectors 38. The lead frame 36 of the body 32 can be included with the body 32 to space and support the plurality of conductors 38 such that contact portions thereof properly electrically connect with the contacts 30 of the plurality of conductors 28 of the plug connector 12, when the connections are mated.
Although the plug 12 and jack 14 above are each shown with eight conductors, one example of a modular connector, which can use only four conductors, is the ubiquitous telephone jack present in almost every home. Typically, however, the plug 12 and jack 14 will each include eight conductors, as shown in FIG. 1B, yielding four data conductor pairs.
The general mechanical design of the modular plug and jack connectors shown FIGS. 1A and 1B was determined at a time when the connectors were to be used almost exclusively for the transmission of relatively low frequency signals, such as analog telephone signals. At the present time, however, modular connectors are used at higher and higher frequencies, such as in computer networks. Unfortunately, at these higher frequencies, cross talk between data pairs of conductors becomes increasingly problematic. It is considered that certain aspects of the mechanical design of the typical modular connector contribute to causing the undesired cross talk.
For example, the conductors 28 of the plug connector 12 are very close and run parallel to each other, such that data conductors that should ideally be electromagnetically isolated from one another actually do interact. Cross talk can be categorized as capacitive, wherein the electric field of conductor of one data pair induces a voltage in a conductor of a different data pair, and inductive, wherein the magnetic field of a conductor of one data pair induces a current in a conductor of a different data pair.
The cross talk in modular connections is often further categorized as near-end cross talk, or NEXT, and far-end cross talk, or FEXT. NEXT refers to cross talk that appears as an unwanted signal in one data pair at, for example, the end 42 of plug connector 12, and is responsive to a signal also entering the end 42 of the plug on another data pair. Such cross talk can be launched onto the external circuit to which the plug connector 12 is electrically connected, such as the computer in FIG. 1A. Similarly, FEXT refers to cross talk that travels through the plug-jack mated pair. For example, for a desired signal entering the end 42 of the plug connector 12 on one data pair, FEXT refers to an undesired signal appearing at the pins 20 and on a different pair of conductors.
Cross talk becomes progressively worse as the frequency of the electrical signals increases. Cross talk standards are promulgated from time to time. Each new standard is typically stricter than the last, such as by increasing the frequency range and/or lowering the amount of allowable cross talk. For example, the Category 5 standard now in use specifies NEXT up to approximately 100 MHz. The Category 5 standard does not address FEXT. The new Category 6 standard specifies cross talk up to a frequency of 250 MHz. Furthermore, the Category 6 standard specifies limits for both NEXT and FEXT.
Because of the large installed base of older modular connectors, and the need for new connector designs to be backwardly compatible with such older connectors installed in the field, the mechanical arrangement of modular connectors is now standard and subject to little change. Accordingly, design choices can be limited, and the focus is on compensating for the cross talk introduced in the connectors. For example, designers have attempted to meet the Category 5 standard by introducing compensating electronic elements into the external circuits to which the plug and jack are connected, or into the jack and/or plug connectors. These elements typically compensate for the cross talk induced in the plug. For example, the conductors of a jack connector can be arranged to introduce inductive cross talk that cancels cross talk introduced in the plug. Also, it is known to provide capacitors on the external circuit 16, such as the printed circuit board of FIG. 1B, to which the output of the jack connector is electrically connected to compensate for cross talk introduced by the plug connector. While such techniques have been useful at lower frequencies, they are not entirely satisfactory, even in the upper frequency range of Category 5. The Category 6 specification significantly exceeds the 100 MHz limit of Category 5 to 250 MHz.
There is an additional complication. Designers are wary to attack the problem of cross talk in the Category 6 frequency range by attacking the source, that is by reducing the cross talk introduced in the plug connector, even apart from the general consideration that much of the mechanical design is fixed. This is because many Category 5 jacks in use meet the Category 5 specification by compensating for a known amount of cross talk in the plug. Remove that cross talk, and the xe2x80x9csolutionxe2x80x9d, that is, the compensation in the Category 5 jack, or in the external circuitry associated with the jack, simply becomes the xe2x80x9cproblemxe2x80x9d, and introduces cross talk when such a jack is mated with a newer plug that introduces less cross talk or that includes it own compensation.
Reducing the cross talk in modular connectors, particularly at higher frequencies, such as above the 100 MHz upper limit of the Category 5 specification, can be problematic.
Accordingly, it is an object of the present invention to address one or more of the foregoing disadvantages and drawbacks of the prior art.
It is another object of the present invention to provide an improved modular connector, such as a modular connector having improved cross talk performance.
In one aspect, the invention provides an improved modular connector such as a jack connector, for mating with another modular connector, such as a plug connector, for electrical connection therewith. The modular connector includes a body and a plurality of conductors disposed with the body. Each of the conductors extends from a first portion to a second end and has a contact portion therebetween, and the contact portions can be substantially parallel and arranged in a row for electrical connection with a row of contacts of the other connector when mated with the modular connector of the invention. The first portions are for connection with an external circuit for communication of signals between the contacts and the external circuit, and are electrically spaced from the contact portions. A capacitive element is disposed with the modular connector and is in electrical communication with a first pair of the conductors, where the electrical communication is established nearer electrically to the contact portions of the conductors than the first portions are to the contact portions.
Preferably, the electrical communication is established at less than about 5 degrees of phase of the contact portions at a selected frequency, such as the highest frequency at which cross talk is to reduced. More preferably, the electrical communication is established at less than about 3 degrees of phase of the contact portions. The selected frequency can be 200 MHz, or alternatively, 250 MHz.
In another aspect of the invention, there is provided a modular connector, such as a jack connector, for mating with a second modular connector of the opposite sex, such as a plug connector, where the second modular connector introduces cross talk having, a predetermined inductive component and a predetermined capacitive component. The modular connector includes a body and a plurality of conductors disposed with the body. Each of the conductors extends from a first portion to a second end and has a contact portion therebetween. The contact portions are substantially parallel and arranged in a row for electrical connection with a row of contacts of the second connector when the modular connector is mated with the second connector. The first portions are for connection with an external circuit for communication of signals between the contacts and the external circuit. Disposed with the connector are a capacitive element and an inductive element. The capacitive and inductive elements are in electrical communication with a first pair of the conductors. The capacitive element provides a capacitive compensation selected to address substantially only the capacitive component of the cross talk, and the inductive element provides an inductive coupling selected to address substantially only the inductive component of the cross talk. Apportioning the compensation in this manner can advantageously help reduce both NEXT and FEXT.
In yet a further aspect of the invention, there is provided a modular connector, such as a jack connector, for mating with a second modular connector of the opposite sex, such as a plug connector, for electrical connection therewith, and where the second modular connector introduces a undesirable cross talk. The modular connector of the invention includes a body and a plurality of conductors disposed with the body, where each of the conductors extends from a first portion to a second end and has a contact portion therebetween. The contact portions are substantially parallel and arranged in a row for electrical connection with a row of contacts of the second connector when the modular connector is mated with the second connector, and the first portions are for connection with an external circuit for communication of signals between the contacts and the external circuit. A capacitive element and an inductive element are both disposed with the connector. The capacitive and inductive elements are in electrical communication with a first pair of the conductors, and the inductive element is not interposed electrically between the capacitive element and the contact portions of the first pair of conductors.
The invention can also include methods than can be practiced in accordance with the teachings herein. For example, in yet an additional feature of the invention, there is provided a method of compensating for cross talk that occurs when a first modular connector mates with a second modular connector that includes a plurality of data pairs and that introduces cross talk between the data pairs. The method includes the following steps:
1) providing the first connector, where first connector includes a plurality of data pairs of conductors, each of the conductors having a contact portion for electrically contacting with a conductor of the other connector when the connectors are mated. Each of the conductors of the first connector extends from a first portion to a second end, with the contact portion being located between the first portion and the second end. The first portions are for connection with an external circuit for communication of signals between the contact portions and the external circuit, and have a predetermined electrical spacing from the contact portions; and
2) disposing a capacitive element with the first connector and in electrical communication with a first pair of the conductors, the pair not being a data pair, and the electrical communication being established nearer electrically to the contact portions of first pair of conductors than the first portions of the first pair of conductors are to the contact portions of the first pair of conductors.
In another aspect of the invention, there is provided a method for compensating for cross talk using a first modular connector when the first modular conductor is mated with a second modular connector that includes a plurality if pairs of data conductors and that introduces cross talk, having a predetermined capacitive component and a predetermined inductive component, between the data pairs. The method can include the steps of:
1) providing a capacitive element that provides a capacitive coupling selected to address substantially only the capacitive component of the cross talk;
2) providing an inductive element that provides an inductive coupling selected to address substantially only the inductive component of the cross talk; and
3) disposing the capacitive and inductive elements with the connector such that each is in electrical communication with a first pair of the conductors, the first pair being other than one of the data pairs.
In yet a further additional feature of the invention, the invention provides a method of compensating for cross talk in modular connector having a plurality of data conductor pairs, where each conductor has a contact portion for contacting; a conductor of the other connector when the connectors are mated. The method can include the steps of:
1) providing a capacitive element;
2) providing an inductive element; and
3) disposing the capacitive and inductive elements with the first connector such that each is in electrical communication with a first pair of the conductors, and such that the inductive element is not interposed electrically between the capacitive element and the contact portions of the conductors of the first pair.
Other features of the invention will be apparent from the present disclosure, including the following Brief Description of The Drawings and Detailed Description Of the Preferred Embodiments.